The micturition reflex is comprised of a plurality of interrelated neurological reflexes involved in urination. The function of the lower urinary tract includes maintenance of urinary continence and periodic expulsion of urine during voiding. The latter functions involve sympathetic, parasympathetic and somatic nerves. Continence is maintainable by sphincter muscles, which preferably controllably contract the bladder urethra, acting as a valve. Discharge of urine is facilitated by sphincter relaxation. Urination also requires coordinated operation of the detrusor muscle which surrounds the bladder. Impairment of one or more of the neurological reflexes associated with proper sphincter or detrusor action can result in inefficient or impaired bladder operation. Damage can occur to the urinary tract as a result of injury or diseases, such as multiple sclerosis. Effective medical treatment can consist of repair or treatment of damaged functional parts by surgical or pharmacological techniques in an attempt to restore the natural sequence of micturition events. Complete restoration of function of course includes returning volitional control of the micturition reflex to the patient. Electronic stimulation techniques are known whereby muscular contractions can be induced in a manner mimicking the natural sequence of events. Thus, knowledge of normal micturition function, including neurological understanding of the lower urinary tract, coupled with an assessment of the damage incurred by the individual patient, facilitates medical treatment of and restoration of function to the neurologically disabled bladder. Diagnosis of a particular patient's micturition characteristics is greatly facilitated through the techniques of gas cystometry and sphincter electromyography.
Cystometry is a diagnostic procedure for evaluating bladder function whereby an accurate picture of normal and abnormal micturition physiology is derived. Cystometric evaluation of micturition disturbances permits an orderly system of classification of neurogenic bladders. The procedure involves distension of the bladder by filling it with a gas or liquid through an inserted catheter. As fluid is inserted interiorly of the bladder, the relation between intravesical bladder pressure and inputted volume of fluid is graphically determined. The principal observation made from the cystometrogram which results in the presence or absence of a detrusor reflex. Where a detrusor reflex is evoked by bladder filling, the patient may be asked to suppress the reflex as a test of detrusor volitional control. The patient's response will be graphically characterized by the cystometrogram (CMG). Cystometry may also be used to test the urodynamics of voiding. The latter technique provides for simultaneous measurement of urinary flow rate with intravesical pressures as voiding occurs concurrently with a detrusor reflex.
Sphinctor electromyography is a diagnostic technique in which micturition electrical responses of the urinary sphincters are graphically displayed. Electromyography has been used in detecting lesions of the lower motor neurons and peripheral nerves and in diagnosing primary skeletal muscle disease. The sphincter response is sensed by utilization of externally contacting electrodes. Usually, electronic amplifying apparatus is provided to process the sphincter signals sensed by the electrodes such that the signal may be displayed; for example, on a strip chart recorder. The electromyogram (EMG) produced by the technique provides a useful graphical monitor of sphincter electrical activity, particularly where a patient is unable to control voiding.
For example, the patient's ability to volitionally contract the sphincters (as is necessary to preserve continence) can be observed by the process to determine if supraspinal innervation is intact. Abnormal patterns of urinary sphincter action, which include detrusor sphinctor dyssynergia and uninhibited urinary sphincter relaxation can also be detected. Thus sphincter electromyography is a useful technique where a patient experiences difficulty with the urinary tract.
Sphincter electromyography is described in an article entitled "Neuro-Urological Selection of Patients for Restoration of the Micturition Reflex", which appears in the book Neuralorganization and Its Relevance to Prosthetics, edited by William S. Fields and published by Intercontinental Medical Book Corp., New York (1973); and in an article entitled "Sphincter Electromyography", appearing in Urologic Clinics of North America, Volume 1, No. 1, published February, 1974. Sphincter monitoring by mechanical devices is disclosed generally in U.S. Pat. No. 3,437,088, entitled "Apparatus for Measuring Esophageal Motility", issued to N. A. Crites on Nov. 25, 1969; and U.S. Pat. No. 2,541,520, entitled "Method and Apparatus to Indicate or Observe Progressive Exercise of Injured Sphincter Muscles", issued to A. H. Kegal on Feb. 13, 1951.
Combining electromyography with cystometry in the evaluation or neuromuscular dysfunction of the lower urinary tract has the potential of providing an understanding of pathophysiological relationships obscure to either technique used alone. For example, the combination of cystometry with concurrent sphincter electromyography facilitates analysis of the two essential elements of voiding, detrusor contraction and sphincter function. See, for example, an article entitled "Cystometric and Sphincter Abnormalities in Multiple Sclerosis", appearing in Neurology, Volume 23, No. 10 (1973). Experimental investigations have demonstrated that increasing bladder distention and detrusor reflex contraction produce attenuation of sphincter EMG activity. For effective voiding sphincter relaxation must occur, but for effective urinary continence reflexive external sphincter contraction must occur. The interaction which occurs during voiding provides for relaxation of the periurethral striated muscle component of the urinary sphincter concurrent with detrusor reflex contractions. With the foregoing background in mind, we have determined the desirability of producing concurrent recording of cystometrographic information and sphincter electromyographic information in order to facilitate diagnostic evaluation of micturition.